The contribution of the pleural membrane to the lung's pressure volume characteristics has been defined. Techniques have been developed for indirectly and directly estimating the magnitude of pulmonary perivascular pressure. Studies are in progress to evaluate the role of perivascular and peribronchial pressure on fluid accumulation in the lung. Video techniques have been used to establish the gradients of regional volume in recumbent dogs. It has been shown that right to left shunting is greater when measured by the oxygen method than by the multiple inert gas technique under general anesthesia. A model of anesthetized supine dog showed changes similar to those in man. It has been shown that halothane and enthurane have different effects on the control of ventilation during anesthesia. Histamine H2 receptors do not occur in dog airways. A nonadrenergic inhibitory system has been identified in the airway smooth muscle of the baboon but not in canine airway smooth muscle. Studies of the determinants of maximal flow in a homogeneous group of nonsmoking males has indicated the importance of static recoil as well as lung volumes an airway resistance in determining maximal flow. In addition, data has been obtained that indicates that airway size may play an important role not only in determining maximum flow but also in determining a normal individual's density dependence.